A sifter of the general type to which the invention relates is known for example from European Patent Specification No. A - 23 320. In that publication the rotor is provided on its upper end face with an annular dispersing plate which encloses a central opening that serves for extraction of the air stream charged with fine material. The material to be sifted is delivered to this dispersing plate by a plurality of material pipes which are arranged on the upper face of the sifter housing around the central pipe which serves for removal of the sifting air. From the edge of the dispersing plate the material is spun radially outwards and deflected downwards by a stationary annular deflecting member in such a way that it falls into the space between the stationary distributor and the rotor.
A significant disadvantage of this known sifter lies in the poor distribution of the material by the dispersing plate. If the material to be sifted is not fed into the sifting chamber completely evenly over the whole periphery then this restricts the precision of separation of the sifter.
The object of the invention, therefore, is to provide a sifter of the general class referred to and which is improved in such manner that, with a simple construction, an absolutely even distribution of the material to be sifted over the whole periphery of the sifting chamber is achieved.